1. Field of the Invention
This invention relates to a resistance change memory device, specifically to a method of stabilizing the resistance change.
2. Description of the Related Art
It has been proposed such a resistance change memory (ReRAM) that stores a resistance value as data, which is reversibly changed by applying voltage, current or heat, and it is noticed for succeeding to the conventional NAND-type flash memory. This resistance change memory is suitable for shrinking the cell size, and for constituting a cross-point cell array. In addition, it is easy to stack cell arrays. Therefore, it is expected of ReRAM to achieve a large capacitive file memory with a three dimensional (3D-) cell array structure.
Especially, a unipolar type of ReRAM cell has such a feature that the high resistance state and low resistance state are reversibly settable by controlling the applied voltage and applying time thereof. For example, refer to Y. Hosoi et al, “High Speed Unipolar Switching Resistance RAM(RRAM) Technology” IEEE International Electron Devices Meeting 2006, Technical Digest, P. 793-796.
To set ReRAM's data (a resistance state) stably, it is in need of precisely controlling the voltage or current to be applied to a cell. This is because of that the cell's resistance is changed drastically while setting the resistance value, and the circuit condition of generating voltage or current also is changed drastically.